RONNIE Biggs won't be freed from prison, Home Secretary Charles Clarke has ruled.

Frail Great Train Robber Biggs, 76, who has had heart tremors and strokes in jail, appealed for "compassionate release".

But on Tuesday Mr Clarke backed prison chiefs' decision not to let him go. He ruled that Biggs was not "severely incapacitated so as to satisfy the criteria".

Biggs learned about the decision in a letter from the National Offender Management Service.

It read: "Whilst noting your frailty and the slow deterioration in your condition, (Mr Clarke) is not persuaded that your condition merits the truly exceptional step of releasing you early on compassionate grounds."

A source said: "Basically Ronnie Biggs is not at death's door and therefore no reason to release him at this stage."

Biggs, who does not come up for parole for another five years, will now only be freed if he gets a life-threatening illness.

Mr Clarke's decision is a bitter blow to Biggs' son Michael, 30, who hoped his father would be transferred from tough, high security Belmarsh prison, South East London, to a secure NHS hospital.

He has no feeling in his face and also got the MRSA superbug after a stint in hospital. Biggs' solicitor Giovanni di Stefano claims Biggs is close to death and it is "inhuman" to keep him locked up.

A Whitehall source said: "The application has been considered seriously and rejected. The advice was that he should not be released on those grounds. If the situation were to change then we would seek further advice."

Biggs got 30 years for his part in the £2.6million raid on the Glasgow to Euston mail train in 1963.

He escaped from prison in 1965 and fled to Australia and then Brazil where he settled down and Michael was born. In 2001 he flew back to Britain and turned himself in because he was ill.

Gangster Reggie Kray was let out of jail after 33 years because he had terminal cancer. He died in hospital a few weeks after his release.